Historically, antiperspirants were made in batches to create different formulations for different products. All batch materials were added consecutively into a large tank and mixed and heated to processing temperature until the next higher melting point material could be added. Once a batch was finished, it needed to be transferred to another tank of equal size to hold as surge for the filling operation. In order to achieve proper mixing for product uniformity, at least a half batch quantity was typically produced, making it difficult to manufacture small production runs. The batch cycle time was very long, typically 7.5 to 9 hours because of the time needed to reach processing temperature and properly mix all materials. Continuous processes have also been used, but the continuous processes have been used to make one formulation with the need to make a change over between formulations. It would be desirable to have a continuous process that could manufacture different formulas without the need for changing over the entire production process. This would result in increased efficiency and the ability to make the desired amount of product.
In an antiperspirant composition, the amount of the antiperspirant active needs to be controlled to its target amount in the composition. In continuous systems, near-infrared (NIR) sensors can be used to measure the amount of a material in a composition. Antiperspirant actives are aluminum containing salts, and they are not detectable by NIR sensors. It would be desirable to manufacture antiperspirant compositions in a continuous process and to control the amount of antiperspirant in the composition.